Field of the Invention
The present invention relates to reduction in dew condensation on a sheet conveying path of an image forming apparatus.
Description of the Related Art
Heretofore, at the time of performing double-sided printing, a sheet whose one side has been printed and the other side will be printed is stopped at a predetermined position of a sheet conveying path in an image forming apparatus. The printing of the other side starts after a control unit of the image forming apparatus receives a paper feed signal. Since the sheet passing a fixing unit stops at the same position for a certain period of time at a position where the sheet is stopped in the image forming apparatus, dew condensation occurs due to water vapor discharged from the sheet, which may cause image defect. Japanese Patent Application Laid-Open No. 2011-191544 discusses a configuration in which a cooling unit to cool a sheet is provided at a position where the sheet stops and the time for which the sheet is stopped is changed to prevent productivity from being lowered.
However, heretofore, there has been only one position where the sheet is stopped at the time of performing double-sided printing, so that it takes a long time for the sheet to stay always at the same standby position. This is liable to cause dew condensation in winter or in a state where the temperature of a conveyance guide is low, such as immediately after a power source is turned on. The time for which water vapor is discharged from the sheet and the quantity of the water vapor discharged therefrom are different depending on air permeance of the sheet, which makes it difficult to propose a configuration which does not cause the dew condensation for all materials only at one standby position. The term “air permeance of the sheet” refers to a degree to which air passes through the sheet in a direction of depth thereof. In addition, if the cooling unit is provided at the position where the sheet is stopped as is conventionally done, which may increase cost.